Self-reported fitness and objectively measured physical activity profile among older adults : a twin study

Background. Maintaining good fitness and good level of physical activity are important factors for maintaining physical independence later in life. The aim was to investigate the relationship between self-reported fitness and objectively measured physical activity and sedentary behavior in the elderly. Methods. Same-sex twin pairs born 1940–1944 in Finland were invited to the study. Altogether 787 individuals (mean age 72.9 years), of whom 404 were female, used a hip-worn triaxial accelerometer for at least 4 days and answered a question on perceived fitness. First, individual differences were studied between four fitness categories. Second, pairwise differences were examined among twin pairs discordant for fitness. Results. Self-reported fitness explained moderately the variation in objectively measured physical activity parameters: R2 for daily steps 26%, for daily mean metabolic equivalent 31%, for daily moderate-to-vigorous activity time 31%, and lower for sedentary behavior time 14% (all p < .001). Better self-reported fitness was associated with more steps taken on average (8,558 daily steps [very good fitness] vs 2,797 steps [poor fitness], p < .001) and with a higher amount of moderate-to-vigorous activity (61 min vs 12 min p < .001, respectively) in the adjusted multivariable model. Among 156 twin pairs discordant for self-reported fitness, co-twins with better fitness took more steps, did more moderate-to-vigorous activity, and had less sedentary behavior (all, p < .05) compared to their less fit co-twins; however, difference was smaller among monozygotic than dizygotic pairs. Conclusion. One simple question on self-reported fitness is associated with daily activity profile among community-dwelling older people. However, genetic factors modulate this association to some extent.peerReviewe